Oil separator and compressed air drying system

ABSTRACT

An oil separator is provided with: a heating device for heating liquid accumulated in a drainage storage section; a connection pipe for connecting the drainage storage section to an external device utilizing oil; an opening and closing device for opening and closing the flow passage of the connection pipe; and a determination device for determining whether or not to deliver the liquid, which is accumulated in the drainage storage section, to the external device. The opening and closing device is configured so as to open the flow passage of the connection pipe when the determination device determines that the liquid accumulated in the drainage storage section is to be delivered to the external device.

CROSS-REFERENCE TO RELATED APPLICATIONS

The subject application is a Divisional Application of U.S. Ser. No. 15/505,794, filed Feb. 22, 2017, which is the U.S. National Stage of PCT/JP2015/074512, filed Aug. 28, 2015, which in turn claims priority to Japanese Patent Application No. JP 2014-176075, filed Aug. 29, 2014, Japanese Patent Application No. JP 2014-176076, filed Aug. 29, 2014, and Japanese Patent Application No. JP 2014-176077, filed Aug. 29, 2014. The contents of each of these applications are incorporated herein by reference in their entireties.

TECHNICAL FIELD

The present invention relates to an oil separator and a compressed-air drying system.

BACKGROUND ART

Vehicles such as trucks, buses, and construction machines use compressed air delivered by a compressor to control systems such as brakes and suspensions. Compressed air delivered by a compressor contains water, which is contained in the atmosphere, and oil for lubricating the inside of the compressor. When the compressed air containing such water and oil enters the systems, it causes rust and swelling of rubber members, resulting in an operational defect of the systems. For this reason, a compressed-air drying system is provided downstream of the above-mentioned compressor to remove water and oil from the compressed air. The compressed-air drying system includes an air dryer that removes water and oil from compressed air by causing the compressed air to pass through a desiccant (see, for example, Patent Document 1).

The air dryer executes a loading mode operation for removing water and oil from compressed air by allowing the compressed air to pass through a desiccant and an unloading mode operation for regenerating the desiccant by ejecting water and oil trapped by the desiccant to the outside. The air ejected from the air dryer during the unloading mode operation contains water and oil. Thus, considering the burden on the environment, a compressed-air drying system has been proposed that has an oil separator in a passage for air ejected from the air dryer. This oil separator separates oil from the air ejected from the air dryer during the unloading mode operation and stores the separated oil.

The oil separator separates gas and liquid from each other by causing air containing water and oil to a strike impingement member. Such gas/liquid separation causes the air from which water and oil have been removed to be expelled to the outside and the water and oil that have been separated from the air to be stored in a liquid storage portion in the oil separator (for example, see Patent Document 2).

PRIOR ART DOCUMENTS Patent Documents

Patent Document 1: Japanese Laid-Open Patent Publication No. 2012-106155

Patent Document 2: Japanese Laid-Open Patent Publication No. 2013-234632

SUMMARY OF THE INVENTION Problems that the Invention is to Solve

In the oil separator described in the above-mentioned Patent Document 1, the liquid containing oil and water separated from air is stored in the liquid storage portion in the oil separator. Thus, when the amount of the stored liquid reaches the volume of the storage portion, the oil separator cannot store more liquid. Thus, the collected liquid needs to be periodically withdrawn from the oil separator. The number of times collected liquid is withdrawn is desired to be small. In this regard, an oil separator has been sought that reduces the number of times the separated liquid is recovered.

Accordingly, it is an objective of the present invention to provide an oil separator that reduces the number of times separated liquid is withdrawn.

Means for Solving the Problems

To achieve the foregoing objective and in accordance with one aspect of the present invention, an oil separator that includes a housing and an impingement member arranged in the housing is provided. The oil separator is configured to introduce air containing oil into the housing, cause the air to strike the impingement member to separate liquid containing the oil from the introduced air, and store the liquid in a liquid storage portion. The oil separator further includes a connecting pipe that connects the liquid storage portion to an external device that utilizes the oil, an opening/closing device that selectively opens and closes a flow path of the connecting pipe, and a determination device that determines whether the liquid stored in the liquid storage portion should be delivered to the external device. The opening/closing device is configured such that, when the determination device determines that the liquid stored in the liquid storage portion should be delivered to the external device, the opening/closing device opens the flow path of the connecting pipe.

In accordance with another aspect of the present invention, an oil separator that includes a housing and an impingement member arranged in the housing is provided. The oil separator introduces air containing oil into the housing and causes the air to strike the impingement member to separate liquid containing the oil from the introduced air and stores the liquid in a liquid storage portion. The oil separate is installed in a vehicle in which a diesel engine is mounted. The liquid storage portion includes an ejection port that is connected to a combustion unit provided in an exhaust purification device that traps particles contained in exhaust gas of the diesel engine. The liquid stored in the liquid storage portion is supplied to the combustion unit of the exhaust purification device.

In accordance with a further aspect of the present invention, a compressed-air drying system that traps water and oil contained in compressed air is provided. The system includes at least one of an air dryer and an oil mist separator and an oil separator. The air dryer is configured to trap water and oil contained in compressed air during a loading mode operation and to eject the trapped water and oil during an unloading mode operation. The oil mist separator is configured to trap oil contained in compressed air during a loading mode operation and to eject the trapped oil during an unloading mode operation. The oil separator is configured to store the ejected water and oil in a liquid storage portion. The oil separator is arranged above the at least one of the air dryer and the oil mist separator in a vertical direction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating an oil separator according to a first embodiment.

FIG. 2 is a block diagram illustrating an oil separator according to a second embodiment.

FIG. 3 is a block diagram illustrating the internal structure of an oil separator according to a third embodiment.

FIG. 4 is a block diagram illustrating a heating device of an oil separator according to a fourth embodiment.

FIG. 5 is a block diagram illustrating an oil separator according to a modification.

FIG. 6 is a block diagram illustrating an oil separator according to a fifth embodiment.

FIG. 7 is a block diagram illustrating an oil separator according to a modification.

FIG. 8 is a block diagram schematically illustrating a compressed-air drying system according to a sixth embodiment.

FIG. 9 is a perspective view illustrating the positions in a tractor of the air dryer and the oil separator of the compressed-air drying system according to the sixth embodiment.

FIG. 10 is a side view illustrating the positions in the tractor of the air dryer and the oil separator of the compressed-air drying system shown in FIG. 9.

FIG. 11 is a side view illustrating the positions in a truck of an air dryer and an oil separator of a compressed-air drying system according to a modification.

MODES FOR CARRYING OUT THE INVENTION First Embodiment

An oil separator according to a first embodiment will now be described with reference to FIG. 1.

As shown in FIG. 1, a vehicle such as a truck, a bus, or a construction machine uses compressed air delivered from a compressor 1 to control systems such as brakes and suspensions. Thus, an air dryer 2, which removes oil and water from compressed air and delivers dried air, is provided downstream of the compressor 1 in an air system. The air dryer 2 incorporates a desiccant. The air dryer 2 executes a loading mode operation for removing water and oil from compressed air by allowing the compressed air to pass through the desiccant and an unloading mode operation for regenerating the desiccant by ejecting water and oil trapped by the desiccant to the outside. The air dryer 2 delivers, to a system tank 4, dry compressed air that has been dried through the loading mode operation. The system tank 4 supplies the compressed air to systems such as brakes and suspensions. When the pressure in the system tank 4 reaches a predetermined value, the governor (not shown) of the air dryer 2 is activated so that control air is introduced to the air dryer 2, which initiates the unloading mode operation. During the unloading mode operation, the control air opens an exhaust valve 2 a. When the exhaust valve 2 a of the air dryer 2 is opened, compressed air flows backward so that air that contains oil as well as water (purge air) is delivered from an ejection port 2 b.

In consideration of the burden on the environment, an oil separator 3 is provided downstream of the compressor 1 in the air system. Specifically, the oil separator 3 is connected to the ejection port 2 b of the air dryer 2 via an air dryer connection hose 20 to separate and store oil and water from the purge air ejected during regeneration of the desiccant in the air dryer 2.

The oil separator 3 is an impingement type oil separator that performs gas/liquid separation. The oil separator 3 has a housing 3 a, in which an impingement member 3 b is provided. Purge air containing oil and water is caused to strike the impingement member 3 b. The impingement type oil separator 3 causes purge air containing oil and water to strike the impingement member 3 b to separate the oil and water from the purge air, thereby ejecting clean air, from which oil and water have been separated, through an ejection port 3 d. The flow path of the purge air from the introduction into the housing 3 a to the impingement with the impingement member 3 b is not particularly limited. For example, the flow path may include a portion for swirling the purge air. In this case, the oil separator 3 may be a cyclonic oil separator. The liquid that contains oil and water separated from the purge air will hereafter be referred to as collected liquid in some cases. The oil separator 3 has a liquid storage portion 3 c, which stores the separated and collected liquid.

When the amount of the stored liquid reaches the volume of the liquid storage portion 3 c, the oil separator 3 cannot store more liquid. In such a case, the oil separator 3 returns collected liquid, for example, to an internal combustion engine 6, which is an external device that utilizes oil. Furthermore, the oil separator 3 heats the collected liquid stored in the liquid storage portion 3 c to vaporize water from the liquid, thereby reducing the ratio of water contained in the collected liquid. In order to sufficiently vaporize the water from the collected liquid, the oil separator 3 holds the collected liquid in the liquid storage portion 3 c until it is determined that the delivery condition is satisfied. When it is determined that the delivery condition is satisfied, the oil separator 3 delivers the collected liquid to the external device from the liquid storage portion 3 c.

The engine 6 has an oil pan 6 a for storing lubricant. The lubricant stored in the oil pan 6 a is circulated within the engine 6 and also circulated within the compressor 1.

The liquid storage portion 3 c of the oil separator 3 is connected to the oil pan 6 a of the engine 6 via a liquid supply hose 30. The collected liquid stored in the liquid storage portion 3 c is supplied to the oil pan 6 a of the engine 6. The liquid supply hose 30 corresponds to a connecting pipe. A control valve 30 a is provided in the liquid supply hose 30. The control valve 30 a is an opening/closing device that selectively opens and closes the passage. The collected liquid stored in the liquid storage portion 3 c is heated by a coolant circuit 40, which functions as a heating device. The coolant circuit 40 is wound about the housing 3 a of the oil separator 3 to transfer heat to the housing 3 a. Coolant that has been heated by absorbing heat from the engine 6 flows through the coolant circuit 40. Heat is transferred to the housing 3 a of the oil separator 3 from the heated coolant, so that the collected liquid in the liquid storage portion 3 c is heated.

The oil separator 3 delivers collected liquid to the oil pan 6 a of the engine 6 when the delivery condition is satisfied, that is, on the condition that the number of times purge air is introduced into the housing 3 a has reached the number necessary to store a predetermined amount of collected liquid. That is, a counter 21 for counting the number of times purge air is ejected is installed at the ejection port 2 b of the air dryer 2. In the present embodiment, the counter 21 functions as a determination device. The counter 21 measures the number of times purge air is introduced into the housing 3 a by measuring the number of times the exhaust valve 2 a is opened. Since approximate values of the amount of purge air ejected by a single opening operation and the ratio of oil and water contained in the purge air are known, the required number of times of introduction is determined based on the predetermined amount of collected liquid. The counter 21 causes the control valve 30 a to open when the number of times purge air is ejected reaches the predetermined number. The counter 21 causes the control valve 30 a to close after a lapse of a fixed time from its opening. The counter 21 keeps the control valve 30 a closed until the number of times purge air is ejected reaches the predetermined number.

Operation of the oil separator configured as described above will now be described with reference to FIG. 1.

With reference to FIG. 1, the compressor 1 generates compressed air through operation of the engine 6 and delivers the compressed air to the air dryer 2. The air dryer 2 executes the loading mode operation to cause the compressed air from the compressor 1 to pass through the desiccant, thereby removing water and oil contained in the compressed air to dry the compressed air. The air dryer 2 then delivers the dry compressed air to the system tank 4. The system tank 4 supplies the compressed air to various systems. When the pressure in the system tank 4 reaches a predetermined value, the governor introduces control air to the air dryer 2, and the air dryer 2 executes the unloading mode operation for regenerating the desiccant. In the unloading mode operation, compressed air flows backward so that purge air that contains oil as well as water is delivered from the ejection port 2 b. The purge air delivered through the ejection port 2 b of the air dryer 2 is introduced to the oil separator 3 via the air dryer connection hose 20.

When receiving purge air, which contains oil and water, the oil separator 3 separates the oil and water from the purge air by causing the purge air to strike the impingement member 3 b provided in the housing 3 a. Clean air from which oil and water have been separated is ejected through the ejection port 3 d. The oil and water separated from the purge air are stored as collected liquid in the liquid storage portion 3 c. Since the liquid storage portion 3 c is wrapped with and heated by the coolant circuit 40, the collected liquid stored in the liquid storage portion 3 c is heated by the coolant circuit 40.

The counter 21 provided for the air dryer 2 counts the number of times purge air is ejected. When the counted number reaches a predetermined number, the counter 21 causes the control valve 30 a to open. When the control valve 30 a is opened, the liquid supply hose 30 is open, so that the collected liquid stored in the liquid storage portion 3 c of the oil separator 3 is supplied into the oil pan 6 a of the engine 6 through the liquid supply hose 30. The counter 21 causes the control valve 30 a to close after a lapse of a fixed time from its opening.

As described above, the water in the collected liquid stored in the liquid storage portion 3 c of the oil separator 3 is reduced by heating the collected liquid with the heated coolant, and the collected liquid, of which the water content has been reduced, is supplied to the oil pan 6 a of the engine 6, which is an external device. Therefore, it is possible to reduce the number of times collected separated liquid in the oil separator 3 is withdrawn. Also, the counter 21 counts the number of times purge air is ejected, and causes the control valve 30 a to open after the counted number reaches a predetermined number of times, so that the collected liquid is delivered to the oil pan 6 a of the engine 6 after a predetermined amount of the collected liquid is stored.

The present embodiment as described above achieves the following advantages.

(1) By delivering the collected liquid stored in the liquid storage portion 3 c of the oil separator 3 to the oil pan 6 a of the engine 6, which utilizes oil, it is possible to reduce the number of times the separated liquid in the oil separator 3 is withdrawn. Also, until the delivery condition is satisfied, collected liquid is stored in the liquid storage portion 3 c and heated to vaporize the water from the collected liquid. This permits collected liquid in which the ratio of water has been reduced to be delivered to the oil pan 6 a of the engine 6.

(2) The counter 21 measures the number of times air containing oil is introduced into the housing 3 a. When the measured number of times of introduction is greater than or equal to the number of times of introduction necessary for a predetermined amount of collected liquid to be stored in the liquid storage portion 3 c, the control valve 30 a opens the flow path of the liquid supply hose 30 and delivers the liquid to the oil pan 6 a of the engine 6. This allows the delivery of collected liquid to be controlled based on the number of times of introduction of air containing oil.

(3) In the case of the oil separator 3 mounted on the vehicle equipped with the engine 6, it is only necessary to route the coolant circuit 40, which is provided in the engine 6, to the oil separator 3. Thus, no additional heating device is required, and the exhaust heat of the engine 6 is effectively utilized.

Second Embodiment

An oil separator according to a second embodiment will now be described with reference to FIG. 2. The oil separator of the present embodiment is different from the first embodiment in that the counter is replaced by a flow rate sensor. Differences from the first embodiment will mainly be discussed below.

As shown in FIG. 2, a flow rate sensor 22, which is a measurement sensor, is arranged at the ejection port 2 b of the air dryer 2. In the present embodiment, the flow rate sensor 22 functions as a determination device. The flow rate sensor 22 measures the amount of the collected liquid in the liquid storage portion 3 c by measuring the amount (ejected amount) of purge air passing through the ejection port 2 b based on the flow rate of the purge air at the ejection port 2 b. The flow rate sensor 22 causes the control valve 30 a to open when the measured ejected amount of the purge air increases and reaches a predetermined amount. Since an approximate value of the amount of oil and water contained in the ejected purge air is known, the predetermined amount of purge air is determined based on a specified amount of the liquid storage portion 3 c. The flow rate sensor 22 causes the control valve 30 a to close after a lapse of a fixed time from its opening. The flow rate sensor 22 keeps the control valve 30 a closed until the measured ejected amount of the purge air reaches the predetermined amount.

Operation of the oil separator configured as described above will now be described with reference to FIG. 2.

As shown in FIG. 2, the flow rate sensor 22 provided for the air dryer 2 measures the ejected amount of purge air, and causes the control valve 30 a to open when the ejected amount reaches the predetermined amount. When the control valve 30 a is opened, the liquid supply hose 30 is open, so that the collected liquid stored in the liquid storage portion 3 c of the oil separator 3 is supplied into the oil pan 6 a of the engine 6 through the liquid supply hose 30. The flow rate sensor 22 causes the control valve 30 a to close after a lapse of a fixed time from its opening.

As described above, the water in the collected liquid stored in the liquid storage portion 3 c of the oil separator 3 is reduced by heating the collected liquid with the heated coolant, and the collected liquid, of which the water content has been reduced, is supplied to the oil pan 6 a of the engine 6, which is an external device. Therefore, it is possible to reduce the number of times collected separated liquid in the oil separator 3 is withdrawn. Also, the flow rate sensor 22 measures the ejected amount of purge air, and causes the control valve 30 a to open after the ejected amount reaches the predetermined amount, so that the collected liquid is delivered to the oil pan 6 a of the engine 6 after a specified amount of the collected liquid is stored.

The present embodiment described above achieves the following advantage in addition to the advantages (1) and (3) of the first embodiment.

(4) By measuring the amount of purge air containing oil ejected from the air dryer 2 with the flow rate sensor 22, the amount of the collected liquid in the liquid storage portion 3 c is measured. When the measured amount of the collected liquid is greater than or equal to the predetermined amount, the control valve 30 a opens the flow path of the liquid supply hose 30 to deliver the collected liquid to the oil pan 6 a of the engine 6. This allows the delivery of collected liquid to be controlled based on the ejected amount of purge air that contains oil.

Third Embodiment

An oil separator according to a third embodiment will now be described with reference to FIG. 3. The oil separator of the present embodiment is different from the first embodiment in that the amount of collected liquid itself stored in the liquid storage portion 3 c of the oil separator is used as the delivery condition. Differences from the first embodiment will mainly be discussed below.

As shown in FIG. 3, the liquid storage portion 3 c of the oil separator 3 has a double structure including an outer container 31 and an inner container 32. The inner container 32 is arranged inside the outer container 31. Collected liquid is stored in the inner container 32. The inner container 32 is supported by the outer container 31 with a spring 33. On the inner bottom of the outer container 31, a weight sensor 34, which is a measurement sensor, is installed. In the present embodiment, the weight sensor 34 functions as a determination device. The weight sensor 34 measures the amount of the collected liquid stored in the liquid storage portion 3 c by measuring the weight of the collected liquid stored in the liquid storage portion 3 c. When a predetermined amount of collected liquid is stored, the inner container 32 is lowered toward the bottom against the urging force of the spring 33, and the weight sensor 34 detects that the predetermined amount of collected liquid has been stored. The weight sensor 34 causes the control valve 30 a to open when the measured weight of collected liquid reaches the predetermined amount. The weight sensor 34 causes the control valve 30 a to close after a lapse of a fixed time from its opening. The flow rate sensor 22 keeps the control valve 30 a closed until the measured weight of the collected liquid reaches the predetermined amount.

Operation of the oil separator configured as described above will now be described with reference to FIG. 2.

As shown in FIG. 2, the weight sensor 34 provided in the oil separator 3 measures the weight of the collected liquid stored in the liquid storage portion 3 c. When the weight reaches the predetermined amount, the weight sensor 34 causes the control valve 30 a to open. When the control valve 30 a is opened, the liquid supply hose 30 is open, so that the collected liquid stored in the liquid storage portion 3 c of the oil separator 3 is supplied into the oil pan 6 a of the engine 6 through the liquid supply hose 30. The weight sensor 34 causes the control valve 30 a to close after a lapse of a fixed time from its opening.

As described above, the water in the collected liquid stored in the liquid storage portion 3 c of the oil separator 3 is reduced by heating the collected liquid with the heated coolant, and the collected liquid, of which the water content has been reduced, is supplied to the oil pan 6 a of the engine 6, which is an external device. Therefore, it is possible to reduce the number of times collected separated liquid in the oil separator 3 is withdrawn. Also, the weight sensor 34 measures the weight of the collected liquid and causes the control valve 30 a to open after the weight reaches the predetermined value, so that the collected liquid is delivered to the oil pan 6 a of the engine 6 after the predetermined amount of the collected liquid is stored.

The present embodiment described above achieves the following advantage in addition to the advantages (1) and (3) of the first embodiment.

(5) The weight sensor 34 measures the amount of the collected liquid stored in the liquid storage portion 3 c by measuring the weight of the collected liquid stored in the liquid storage portion 3 c. When the measured amount of the collected liquid is greater than or equal to the predetermined amount, the control valve 30 a opens the flow path of the liquid supply hose 30 to deliver the collected liquid to the oil pan 6 a of the engine 6. This allows the delivery of collected liquid to be controlled based on the amount of the collected liquid stored in the liquid storage portion 3 c.

Fourth Embodiment

An oil separator according to a fourth embodiment will now be described with reference to FIG. 4. The oil separator of the present embodiment is different from the first embodiment in that the ratio of water (water ratio) contained in the collected liquid stored in the liquid storage portion 3 c of the oil separator is used as the delivery condition. Differences from the first embodiment will mainly be discussed below.

As shown in FIG. 4, a water sensor 35 for measuring the ratio of water in the collected liquid is installed in the liquid storage portion 3 c of the oil separator 3. In the present embodiment, the water sensor 35 functions as a determination device. The water sensor 35 causes the control valve 30 a to open when the measured ratio of water has decreased to a predetermined value. The water sensor 35 causes the control valve 30 a to close after a lapse of a fixed time from its opening. The water sensor 35 keeps the control valve 30 a closed until the measured ratio of water becomes the predetermined value.

The coolant circuit 40 is not wound around the liquid storage portion 3 c. A fin member 41 is arranged at a position opposed to a side of the liquid storage portion 3 c. When the heated coolant passes through the fin member 41, heat is radiated from the fin portion of the fin member 41, and the radiated heat heats the liquid storage portion 3 c.

Operation of the oil separator configured as described above will now be described with reference to FIG. 4.

As shown in FIG. 4, the water sensor 35 provided in the oil separator 3 measures the ratio of water in the collected liquid stored in the liquid storage portion 3 c. When the ratio of water becomes the predetermined value, the water sensor 35 causes the control valve 30 a to open. When the control valve 30 a is opened, the liquid supply hose 30 is open, so that the collected liquid stored in the liquid storage portion 3 c of the oil separator 3 is supplied into the oil pan 6 a of the engine 6 through the liquid supply hose 30. The water sensor 35 causes the control valve 30 a to close after a lapse of a fixed time from its opening.

As described above, the water in the collected liquid stored in the liquid storage portion 3 c of the oil separator 3 is reduced to the amount corresponding to the predetermined ratio of water by heating the collected liquid with the heated coolant, and the collected liquid, in which the water has been reduced, is supplied to the oil pan 6 a of the engine 6, which is an external device. Therefore, it is possible to reduce the number of times collected separated liquid in the oil separator 3 is withdrawn. Also, the water sensor 35 measures the ratio of water in the collected liquid, and causes the control valve 30 a to open after the ratio of water becomes the predetermined value, so that the collected liquid is delivered to the oil pan 6 a of the engine 6 after the amount water in the collected liquid is decreased to the amount corresponding to the predetermined ratio of water.

The present embodiment described above achieves the following advantage in addition to the advantages (1) and (3) of the first embodiment.

(6) The water sensor 35 measures the ratio of water contained in the collected liquid stored in the liquid storage portion 3 c. When the ratio of water contained in the collected liquid is less than or equal to the predetermined value, the control valve 30 a opens the flow path of the liquid supply hose 30 and delivers the liquid to the oil pan 6 a of the engine 6. This allows the delivery of collected liquid to be controlled based on the ratio of water contained in the collected liquid stored in the liquid storage portion 3 c.

The above described first to fourth embodiments may be modified as follows.

In the first embodiment, the counter 21 measures the number of times the exhaust valve 2 a is opened. However, the number of times the purge air passes through the ejection port 2 b may be measured.

The third embodiment may be modified such that the weight sensor 34 measures the weight of the collected liquid stored in the liquid storage portion 3 c, and the control valve 30 a is opened when the measured weight reaches a predetermined value.

In the third embodiment, the weight of the collected liquid stored in the liquid storage portion 3 c is measured. However, a sensor may be provided that detects whether the volume of the collected liquid stored in the liquid storage portion 3 c has reached a predetermined value.

In the first to fourth embodiments, the respective sensors cause the control valve 30 a to close after a lapse of a fixed time from its opening. However, the control valve 30 a may be configured to close after a lapse of a fixed time from its opening.

In the first to third embodiments, the coolant circuit 40 is wound about the liquid storage portion 3 c. However, as in the fourth embodiment, a fin member 41 may be provided. The fin member 41 may be provided after the coolant circuit 40 is wound around the liquid storage portion 3 c.

In the fourth embodiment, the fin member 41 is provided. However, as in the first to third embodiments, the coolant circuit 40 may be wound about the liquid storage portion 3 c. The fin member 41 may be provided after the coolant circuit 40 is wound around the liquid storage portion 3 c.

In the first to fourth embodiments, the coolant circuit 40 of the engine 6 is employed as a heating device. However, as shown in FIG. 5, instead of the coolant circuit 40, a compressed air supply hose 10, or a supply pipe through which compressed air generated by the compressor 1 passes, may be employed as a heating device. In the case of the oil separator 3 mounted on a vehicle equipped with the compressor 1, it only requires that the compressed air supply hose 10, through which compressed air generated by the compressor 1 passes, be routed into the oil separator 3. Thus, no additional heating device is required, and the heat of the compressed air is effectively utilized.

In the first to fourth embodiments, in addition to or instead of the coolant circuit 40, an additional heating device such as an electric heater may be provided in the liquid storage portion 3 c.

Fifth Embodiment

An oil separator according to a fifth embodiment will now be described with reference to FIG. 6.

As shown in FIG. 6, a vehicle such as a truck, a bus, or a construction machine uses compressed air delivered from a compressor 101 to control systems such as brakes and suspensions. Thus, an air dryer 102, which removes oil and water from compressed air and delivers dried air, is provided downstream of the compressor 101 in an air system. The air dryer 102 incorporates a desiccant. The air dryer 102 executes a loading mode operation for removing water and oil from compressed air by allowing the compressed air to pass through the desiccant and an unloading mode operation for regenerating the desiccant by ejecting water and oil trapped by the desiccant to the outside. The air dryer 102 delivers, to a system tank 104, dry compressed air that has been dried through the loading mode operation. The system tank 104 supplies the compressed air to systems such as brakes and suspensions. When the pressure in the system tank 104 reaches a predetermined value, the governor (not shown) of the air dryer 102 is activated so that control air is introduced to the air dryer 2, which initiates the unloading mode operation. During the unloading mode operation, the control air opens an exhaust valve 102 a. When the exhaust valve 102 a of the air dryer 102 is opened, compressed air flows backward so that air that contains oil as well as water (purge air) is delivered from an ejection port 102 b.

In consideration of the burden on the environment, an oil separator 103 is provided downstream of the compressor 101 in the air system. Specifically, the oil separator 103 is connected to the ejection port 102 b of the air dryer 102 via an air dryer connection hose 120 to separate and store oil and water from the purge air ejected during regeneration of the desiccant in the air dryer 102.

The oil separator 103 is an impingement type oil separator that performs gas/liquid separation. The oil separator 103 has a housing 103 a, in which an impingement member 103 b is provided. Purge air containing oil and water is caused to strike the impingement member 103 b. The impingement type oil separator 103 causes purge air containing oil and water to strike the impingement member 103 b to separate the oil and water from the purge air, thereby ejecting clean air, from which oil and water have been separated, through an ejection port 103 d. The flow path of the purge air from the introduction into the housing 103 a to the impingement with the impingement member 103 b is not particularly limited. For example, the flow path may include a portion for swirling the purge air. In this case, the oil separator 103 may be a cyclonic oil separator. The liquid that contains oil and water separated from the purge air will hereafter be referred to as collected liquid in some cases. The oil separator 103 has a liquid storage portion 103 c, which stores the separated and collected liquid.

When the amount of the stored liquid reaches the volume of the liquid storage portion 103 c, the oil separator 103 cannot store more liquid. In such a case, the oil separator 103 returns the collected liquid to an external device that utilizes oil. Furthermore, the oil separator 103 heats the collected liquid stored in the liquid storage portion 103 c to vaporize water from the liquid, thereby reducing the ratio of water contained in the collected liquid. The oil separator 103 delivers the collected liquid to the external device from the liquid storage portion 103 c.

An engine 106 is a diesel engine. Therefore, an exhaust pipe 106 a of the engine 106 is provided with an exhaust purification device 107 that traps particles contained in exhaust gas. The exhaust purification device 107 includes a diesel particulate filter 107 a for trapping particulate matter and a combustion unit 107 b for raising the temperature of exhaust. The combustion unit 107 b raises the temperature of exhaust gas by burning fuel. The exhaust gas, of which the temperature has been raised in the combustion unit 107 b, oxidizes particulate matter and removes it from the diesel particulate filter 107 a.

The liquid storage portion 103 c of the oil separator 103 is connected to the combustion unit 107 b of the exhaust purification device 107 via a liquid supply hose 130. The collected liquid stored in the liquid storage portion 103 c is supplied to the combustion unit 107 b of the exhaust purification device 107. The combustion unit 107 b burs the supplied liquid as fuel to increase the temperature of exhaust gas. The liquid supply hose 130 is provided with a check valve 130 a for preventing backflow. The collected liquid stored in the liquid storage portion 103 c is heated by a compressed air supply hose 110, which functions as a heating device. The compressed air supply hose 110 is wound about the housing 103 a of the oil separator 103 and is configured to transfer heat to the housing 103 a. Air that has been compressed by the compressor 101 passes through the compressed air supply hose 110. Heat is transferred to the housing 103 a of the oil separator 103 from the compressed air, which has been heated through compression, so that the collected liquid in the liquid storage portion 103 c is heated. This promotes vaporization of the water contained in the collected liquid.

Operation of the oil separator configured as described above will now be described with reference to FIG. 6.

With reference to FIG. 6, the compressor 101 generates compressed air through operation of the engine 106 and delivers the compressed air to the air dryer 102. The air dryer 102 executes the loading mode operation to cause the compressed air from the compressor 101 to pass through the desiccant, thereby removing water and oil contained in the compressed air to dry the compressed air. The air dryer 2 then delivers the dry compressed air to the system tank 104. The system tank 104 supplies the compressed air to various systems. When the pressure in the system tank 104 reaches a predetermined value, the governor introduces control air to the air dryer 102, and the air dryer 2 executes the unloading mode operation for regenerating the desiccant. In the unloading mode operation, compressed air flows backward so that purge air that contains oil as well as water is delivered from the ejection port 102 b. The purge air delivered through the ejection port 102 b of the air dryer 102 is introduced to the oil separator 103 via the air dryer connection hose 120.

When receiving purge air, which contains oil and water, the oil separator 103 separates the oil and water from the purge air by causing the purge air to strike the impingement member 103 b provided in the housing 103 a. Clean air from which oil and water have been separated is ejected through the ejection port 103 d. The oil and water separated from the purge air are stored as collected liquid in the liquid storage portion 103 c. Since the liquid storage portion 103 c is wrapped with and heated by the compressed air supply hose 110, the collected liquid stored in the liquid storage portion 103 c is heated by the compressed air supply hose 110.

The collected liquid stored in the liquid storage portion 103 c of the oil separator 103 is supplied to the combustion unit 107 b of the exhaust purification device 107 via the liquid supply hose 130. The combustion unit 107 b burns the collected liquid as fuel to increase the temperature of exhaust gas.

As described above, the collected liquid stored in the liquid storage portion 103 c of the oil separator 103 is heated with compressed air to reduce the water in the collected liquid. The collected liquid is then supplied to the combustion unit 107 b of the exhaust purification device 107, which is an external device. This reduces the number of times the collected liquid that has been separated from the purge air and stored by the oil separator 103 is withdrawn.

The fifth embodiment as described above achieves the following advantages.

(7) By delivering the collected liquid stored in the liquid storage portion 103 c of the oil separator 103 to the combustion unit 107 b of the exhaust purification device 107, which utilizes oil, it is possible to reduce the number of times the collected liquid that has been separated from the purge air and stored by the oil separator is withdrawn. Also, the configuration reduces the amount of fuel used by the combustion unit 107 b of the exhaust purification device 107, which improves the fuel economy.

(8) The collected liquid stored in the liquid storage portion 103 c of the oil separator 103 is heated to vaporize water in the collected liquid. This allows the collected liquid, in which the ratio of water has been reduced, to be supplied to the combustion unit 107 b of the exhaust purification device 107.

(9) In the case of the oil separator 103 mounted on a vehicle equipped with the compressor 101, it only requires that the compressed air supply hose 110, through which compressed air generated by the compressor 101 passes, be routed into the oil separator 103. Thus, no additional heating device is required, and the heat of the compressed air is effectively utilized.

The fifth embodiment may be modified as follows.

In the fifth embodiment, the collected liquid in the liquid storage portion 103 c is heated with compressed air. However, the collected liquid in the liquid storage portion 103 c may be heated with coolant that has been heated through cooling the engine 106.

In the fifth embodiment, a heating device such as an electric heater may be provided in the liquid storage portion 103 c.

As shown in FIG. 7, the fuel for the combustion unit 107 b of the exhaust purification device 107 is not limited to the collected liquid stored in the liquid storage portion 103 c. However, fuel from a fuel tank may be supplied and mixed with the collected liquid. That is, a fuel supply hose 190 connected to the fuel tank 109 is connected to the liquid supply hose 130. Further, a detection sensor 191 for detecting the state of mixed fuel may be provided, and the supply amount of the fuel from the fuel tank 109 may be controlled by a control valve 192 based on the detected state of the fuel. For example, a water sensor may be employed as the detection sensor 191. In this case, the ratio of oil contained in the collected liquid supplied to the combustion unit 107 b of the exhaust purification device 107 can be increased by mixing the collected liquid and the oil, which is fuel. This improves the combustion efficiency.

Sixth Embodiment

Since an air dryer is often installed together with various devices, the installation space for an oil separator is limited around the air dryer. In addition, since an oil separator is often retrofitted to remove oil contained in the gas discharged by the air dryer, the installation space for the oil separator is not taken into consideration. In the compressed-air drying systems described in Patent Documents 1 and 2, the installation positions of the air dryer and the oil separator are not discussed. Thus, a compressed-air drying system is desired in which an air dryer and an oil separator are located at optimal positions.

The present embodiment provides a compressed-air drying system in which an air dryer and an oil separator are located at optimal positions.

A compressed-air drying system according to the sixth embodiment will now be described with reference to FIGS. 8 to 10. In the sixth embodiment, the compressed-air drying system is employed in a tractor.

As shown in FIG. 8, a tractor that tows a trailer uses compressed air delivered from a compressor 201 to control systems such as brakes and suspensions. A compressed-air drying system for removing oil and water from compressed air is provided downstream of the compressor 201. The compressed-air drying system includes an air dryer 202, which dries compressed air by removing oil and water from the compressed air. The air dryer 202 incorporates a desiccant 202 c. The air dryer 202 executes a loading mode operation for removing water and oil from compressed air by allowing the compressed air to pass through the desiccant 202 c and an unloading mode operation for regenerating the desiccant 202 c by ejecting water and oil trapped by the desiccant 202 c to the outside. The air dryer 202 delivers, to a system tank 204, dry compressed air that has been dried through the loading mode operation. The system tank 204 supplies the compressed air to systems such as brakes and suspensions. When the pressure in the system tank 204 reaches a predetermined value, the unloading mode operation is executed. During the unloading mode operation, an exhaust valve 202 a of the air dryer 202 is opened. When the exhaust valve of the air dryer 202 is opened, compressed air flows backward so that air that contains oil as well as water (purge air) is delivered from an ejection port 202 b. In other words, the air dryer 202 ejects the trapped water and oil with the backflow of compressed air.

In consideration of the burden on the environment, the compressed-air drying system includes an oil separator 203, which is provided at the ejection port 202 b of the air dryer 202. The oil separator 203 is connected to the ejection port 202 b of the air dryer 202 via an air dryer connection hose 220 to separate and store oil and water from the purge air ejected during regeneration of the desiccant 202 c in the air dryer 202.

The oil separator 203 is an impingement type oil separator that performs gas/liquid separation. The oil separator 203 has a housing 203 a, in which an impingement member 203 b is provided. Purge air containing oil and water is caused to strike the impingement member 203 b. The impingement type oil separator 203 causes purge air containing oil and water to strike the impingement member 203 b to separate the oil and water from the purge air, thereby ejecting clean air, from which oil and water have been separated, through an ejection port 203 d. The flow path of the purge air from the introduction into the housing 203 a to the impingement with the impingement member 203 b is not particularly limited. For example, the flow path may include a portion for swirling the purge air. In this case, the oil separator 203 may be a cyclonic oil separator. The liquid that contains oil and water separated from the purge air will hereafter be referred to as collected liquid in some cases. The oil separator 203 has a liquid storage portion 203 c, which stores the separated and collected liquid.

As shown in FIGS. 9 and 10, the tractor 210 is capable of traveling on its own and thus has front wheels WF and rear wheels WR. Above the front wheels WF, a cab 211 is provided, which includes a driver's seat and a passenger seat. A loading platform 214 is provided on side frames 212 at a position from behind the cab 211 to above the rear wheels WR. A top board 213, on which articles are loaded, is placed on the loading platform 214.

The oil separator 203 of the compressed-air drying system is located above the air dryer 202 of the compressed air-drying system in the vertical direction. That is, the air dryer 202 is installed below the top board 213, and the oil separator 203 is installed above the top board 213. The system tank 204 is fixed below the top board 213. The air dryer 202 is fixed to the system tank 204.

The oil separator 203 is fixed to the top board 213 with a support member 205. The support member 205 is an L-shaped plate. The support member 205 has a fixed portion 205 a, which faces the top board 213 and is fixed to the top board 213 with bolts. The oil separator 203 has a housing 203 a and an attachment portion 203 e for fixation. The attachment portion 203 e is integrated with the housing 203 a. The support member 205 has a support portion 205 b, which extends upward from the top board 213. The attachment portion 203 e of the oil separator 203 is fixed to the support portion 205 b with bolts. Since there is almost no available space around the air dryer 202, installation of the oil separator 203 is facilitated by arranging it above of the top board 213.

Operation of the compressed-air drying system configured as described above will now be described with reference to FIGS. 8 to 10.

With reference to FIGS. 8 to 10, the compressor 201 generates compressed air through operation of the engine and delivers the compressed air to the air dryer 202. The air dryer 202 executes the loading mode operation to cause the compressed air from the compressor 201 to pass through the desiccant 202 c, thereby removing water and oil contained in the compressed air to dry the compressed air. The air dryer 202 then delivers the dry compressed air to the system tank 204. The system tank 204 supplies the compressed air to various systems. When the pressure in the system tank 204 reaches a predetermined value, the air dryer 202 executes the unloading mode operation to regenerate the desiccant 202 c. In the unloading mode operation, compressed air flows backward so that purge air that contains oil as well as water is delivered from the ejection port 202 b. The purge air delivered through the ejection port 202 b of the air dryer 202 is introduced to the oil separator 203 via the air dryer connection hose 220. The purge air is delivered to the oil separator 203 located above the air dryer 202 in the vertical direction by the pressure of the compressed air.

When receiving purge air, which contains oil and water, the oil separator 203 separates the oil and water from the purge air by causing the purge air to strike the impingement member 203 b provided in the housing 203 a. Clean air from which oil and water have been separated is ejected through the ejection port 203 d. The oil and water separated from the purge air are stored as collected liquid in the liquid storage portion 203 c.

As described above, since the oil separator 203 is easily installed above the air dryer 202 in the vertical direction, the air dryer 202 and the oil separator 203 can be installed at optimal positions.

The sixth embodiment as described above achieves the following advantages.

(10) The area surrounding the air dryer 202 is occupied by the existing devices and provides thus no installation space. Thus, arranging the oil separator 203 above the air dryer 202 in the vertical direction, where a relatively large installation space exists, facilitates the installation. This also allows the air dryer 202 and the oil separator 203 to be located at optimal positions.

(11) The oil separator 203 is installed on the upper side of the top board 213, on which articles are loaded. This ensures that the installation space for the oil separator 203 be provided, and thus facilitates the installation of the oil separator 203. In addition, since the upper side of the top board 213 is a position where the operator does not need to bend over when withdrawing the collected liquid from the oil separator 203. This facilitates the withdrawing operation.

(12) Since the oil separator 203 is fixed to the top board 213 via the support member 205, the oil separator 203 is reliably installed on the top board 213.

The sixth embodiment may be modified as follows.

In the sixth embodiment, the compressed-air drying system is employed in the tractor 210, which tows a trailer. However, the compressed-air drying system may be employed in vehicles such as trucks, buses, and construction machines. For example, as shown in FIG. 11, the oil separator 203 may be installed between a cab 231 of a track 230 and a body 235 serving as a cargo space. A loading platform 234 is provided above side frames 232. A top board 233 is placed on the loading platform 234. The oil separator 203 is fixed to the top board 233 with a support member 205 fixed to the top board 233.

In the sixth embodiment, the present invention is applied to vehicles having top boards 213, 233. However, even in a vehicle having no top board, the oil separator 203 may be installed to be located above the air dryer 202 in the vertical direction.

In the sixth embodiment, an oil mist separator may be provided between the compressor 201 and the air dryer 202. During the loading mode operation, the oil mist separator traps oil contained as oil mist in compressed air introduced from the compressor 201. During the unloading mode operation, the oil mist separator ejects collected liquid containing the trapped oil to the oil separator 203. The oil in the ejected oil mist is stored in a liquid storage portion 203 c of the oil separator 203. If an oil mist separator is provided between the compressor 201 and the air dryer 202, the air dryer 202 does not necessarily need to be connected to the oil separator 203. 

1. A compressed-air drying system that traps water and oil contained in compressed air, the system comprising: at least one of an air dryer and an oil mist separator, wherein the air dryer is configured to trap water and oil contained in compressed air during a loading mode operation and to eject the trapped water and oil during an unloading mode operation, and the oil mist separator is configured to trap oil contained in compressed air during a loading mode operation and to eject the trapped oil during an unloading mode operation; and an oil separator that is configured to store the ejected water and oil in a liquid storage portion, wherein the oil separator is arranged above the at least one of the air dryer and the oil mist separator in a vertical direction.
 2. The compressed-air drying system according to claim 1, wherein the air dryer is configured to eject air containing the trapped water and oil to the oil separator during the unloading mode operation, and the oil separator is configured to separate water and oil from the ejected air and store the separated water and oil in the liquid storage portion.
 3. The compressed-air drying system according to claim 1, wherein the compressed-air drying system is mounted in a vehicle having a loading platform, the at least one of the air dryer and the oil mist separator is installed below a top board of the loading platform, and the oil separator is installed above the top board.
 4. The compressed-air drying system according to claim 3, wherein the oil separator is fixed to the top board with a support member. 